The Eifel lies between the cities of Aachen to the north, Trier to the south and Koblenz to the east. It descends in the northeast along a line from Aachen via Düren to Bonn into the Lower Rhine Bay. In the east and south it is bounded by the valleys of the Rhine and the Moselle. To the west it transitions in Belgium and Luxembourg into the geologically related Ardennes and the Luxembourg Ösling. In the north it is limited by the Jülich-Zülpicher Börde. Within Germany it lies within the states of Rhineland-Palatinate and North Rhine-Westphalia; in BeNeLux the area of Eupen, St. Vith and Luxembourg. Its highest point is the volcanic cone of the Hohe Acht (746.9 m). Originally the Carolingian Eifelgau only covered the smaller region roughly around the sources of the rivers Ahr, Kyll, Urft and Erft. Its name was more recently transferred to the entire region.

South of the Ahr is the High Eifel[1] (Hohe Eifel), with the Hohe Acht (747 m) being the highest mountain of the Eifel.

In the west, on the Belgian border, the hills are known as Schneifel (part of the Schnee-Eifel or "Snowy Eifel"), rising up to 698 m. Also in the west, by the Belgian and Luxembourg border, the region is known as Islek (Aquilania).

The southern half of the Eifel is lower. It is cut by several rivers running north-south towards the Moselle. The largest of these is the Kyll, and the hills on either side of this river are called the Kyllwald.

In the south the Eifel is concluded by the Voreifel above the Moselle.

Due to its moist and mild Atlantic climate, the Eifel bisected by numerous streams and small rivers. Impoundment of these streams, especially in the North Eifel has led to the creation of very large reservoir, such as the Rursee, which is the second largest in Germany by volume, and the Urftsee.

A feature of the Eifel are its natural lakes of volcanic origin. The largest, the Laacher See, is a collapsed, water-filled caldera, whilst the many maars are water-filled volcanic eruption bowls. The largest maar lake is the Pulvermaar. The Meerfelder Maar has an even bigger basin, but three-quarters of it has silted up.

The many rivers and streams of the Eifel drain into the North Sea via the great rivers outside of the Eifel: the Rhine (and its tributary, the Moselle) and the Meuse (with its tributaries, the Rur and Ourthe). The rivers and streams within the mountain range, together with their larger tributaries, are as follows:

In the Tertiary and Quaternary geological eras, the Eifel was a site of extensive volcanic activity. Some of the hills are volcanic vents. The peculiar circle-shaped lakes (maars) of the volcanic regions formed in volcanic craters. The last volcanic eruptions in the Laacher See volcanic site took place around 10,000 years ago and generated a huge volume of volcanic ash, now found in thin ash layers in contemporaneous sediments throughout Europe. The volcanism of the Eifel is thought to be partly caused by the Eifel hotspot, a place where hot material from deep in the mantle rises to the surface, and partly by melt-ascent at deep fractures in the Earth's crust.[3] Research has shown that the volcanism is still active; the Eifel region is rising by 1–2 mm per year.

Historically, the Eifel volcanoes had inactive phases of 10,000 to 20,000 years between active phases, suggesting there is a possibility of future eruptions.[citation needed]

The Nürburgring, one of the world's most famous motor-racing courses. The northern loop (Nordschleife) of the course is known as the Green Hell (Grüne Hölle), because of its long, difficult and dangerous course through the local forest.